Ice-rafted debris of Late Cenozoic sediments from ODP Leg 104 holes@en

The abundance and composition of the upper Cenozoic terrigenous coarse-sand fraction (250 µm-2 mm) at ODP Sites 642, 643, and 644 were investigated to date the onset of significant ice-rafting in the Norwegian Sea, establish the regional chronology of ice-rafting, and determine the relative importance of global vs. regional controls on ice-rafting in this area. The first input of ice-rafted debris (IRD) occurs at approximately 2.9 Ma, with significant ice-rafting beginning at about 2.5 Ma. IRD abundances increase significantly in sediments younger than 0.9 Ma at all three holes, indicating climatic deterioration in the late Pleistocene. Differences in the timing of this IRD increase between holes result from regional patterns of IRD supply and surface circulation. Variations in IRD sources and dispersal patterns may also explain the slightly higher background level of IRD abundance at Hole 642B, a seaward site. […]本研究针对大洋钻探计划（Ocean Drilling Program, ODP）642、643及644站位的晚新生代陆源粗砂组分（粒径250 μm~2 mm）的丰度与组成展开调查，以期厘定挪威海大规模冰筏沉积的起始时间，建立区域冰筏沉积年代序列，并厘清全球与区域因素对该区域冰筏沉积的相对影响程度。冰筏碎屑（ice-rafted debris, IRD）的首次输入出现于约2.9 Ma，而大规模冰筏沉积则始于约2.5 Ma。在三个钻井孔的0.9 Ma以来的沉积物中，IRD丰度均显著升高，指示晚更新世气候恶化。不同钻井孔间IRD丰度升高的时间差异，源于IRD供给与表层环流的区域分布格局。642B站位作为离岸站位，其背景IRD丰度略高的现象，同样可通过IRD物源与扩散模式的差异加以解释。[…]